The elimination of pain, although of obvious importance, is not the primary role of an anesthesiologist. The anesthesiologist's foremost task involves maintaining an equilibrium of the functions of vital organs in the face of disequilibrating effects of disease, surgery, and pharmacologic interventions, including anesthesia. This balance is preserved through frequent measurements and adjustments of respired and blood gases, respiratory rate, blood pressure, heart rate, and other vital signs. Continuous and fast monitoring of inspired and expired anesthesia gases can significantly improve the efficacy of the procedure, satisfying the increasing demands of modern surgery and significantly improving the quality of care.
Another convincing argument for the continuous anesthesia monitoring is patient safety. In 1988, the nine hospitals affiliated with Harvard Medical School undertook a retrospective study of the last 12 years and found that some $5 million in projected insurance payouts could have been prevented in their own institutions, if patient monitoring had been routinely used. Furthermore, it found that the rate of accidents in anesthesia fell threefold when minimum monitoring standards for every anesthetic administered were made mandatory in 1985.
The three most commonly used anesthetic agents are volatile halogenated organic compounds: Halothane (Fluothane.RTM., Wyeth-Ayerst Labs., Philadelphia, Pa.), Enflurane (Ethrane.RTM., Ohmeda, Madison, Wis.), and Isoflurane (Forane.RTM., Ohmeda, Madison, Wis.). Two new agents have recently been developed, Desflurane (Suprane.RTM., Ohmeda, Madison, Wis.) and Sevoflurane (Abbott, Abbott Park, Ill.). In clinical anesthesia, the vapors of these agents are mixed into the breathing mixture with the use of calibrated vaporizers. Only one anesthetic agent is used at a time. The agent concentration in the breathing circuit mixture may range from 0 to 5% for Halothane, Sevoflurane, and Isoflurane, 0 to 7% for Enflurane, and 0-18% for Desflurane.
There are a few available technologies capable of measuring and identifying anesthetic gas. Mass spectrometry was the first methodology used clinically that provided accurate analysis of all of the gases and agents used in anesthesia. In another technology, Raman spectrometer, a powerful UV laser beam is reflected many times across the gas sample and Raman scattered light is detected at right angles to the laser beam. Infra-red spectroscopy analyzes multiple infra-red wave bands to identify specific anesthetic agents.